1. Field of the Invention
The invention relates to a controller for controlling a non-linear mechanical system having a plurality of degrees of freedom.
2. Description of the Related Art
A degree of freedom is a possibility of the mechanical system to move in a certain direction, like a translation along an x-,y- and/or z-axis or a rotation around an x-,y- and/or z-axis. A mechanical system can have a plurality of degrees of freedom, which need to be controlled to obtain a desired position or rotation.
Such a controller is used to realise for example accurate positioning of a mechanical system. Examples of such mechanical systems can be found in both consumer products (so-called CD-players, DCC-players) and in industrial production equipment (wafersteppers, component-placement-equipment). Many mechanical systems are subject to friction and/or backlash, which makes it difficult to position the mechanical system accurately. Instead of demanding higher accuracy of the mechanical system, which inevitably leads to more expensive components, a controller can be used. However, controllers which control the non-linear aspects of the mechanical system, like friction and backlash, and which accurately position a mechanical system are not known.